As the sail together with the propeller is the most prominent part of the submarine in my opinion a wanted to add a ton of details to it.
The VICTOR III sail has a lot of louvers and hatches. Early in the design I decided to leave every hatch opening open and fabricate the hatches separately. That way customers can decide to put the hatch in an open or closed position, whatever he prefers.
They ore also a lot of cameras in the sail which are protected by an acrylic sheet. To match that I also provided openings in those places and I will cast the parts in clear resin so they can be glued in place after the customers have painted their submarine. This will provide an awesome detail, matching the acrylic panels of the real sub.
I will go through the whole process of the sail master, the fabrication the silicone tooling and the casting of the sail.
Below picture is the printed fwd piece of the sail, I had the print the sail in two pieces due to the print limited print aria of the printer.
Test fitting the sail on the hull.
One of the 10 louvres pieces.
The separate hatches and doors.
Test fitting hatches and doors
The indicated inserts are the parts that represent the by acrylic protected cameras and will later casted in clear resin.
The louvres were glued in place and I scribed a recess around them to let them pop out.
For those who don’t know what scribing means please find below the explanation I stole from David Merriman
“SCRIBING This is the process of scraping (abrading) engraved, often narrow, depressions into the work. Most suited to representing seams between plates in close proximity to each other, such as access panels, hatch or door outlines, safety-track, missile hatches, even cheat-lines (waterlines, centerlines, datum lines, etc.), and breaks between fixed structure and control surfaces.”
A coat of filler was applied and wet sanded down, this revealed all the small artifact you due to the 3D printing process, it is impossible to avoid them. After the process op paint ant sanding most of them are filled with paint.
Maybe you noticed in the previous picture that the hole pattern (think it’s a SOKS item) was not complete, it bothered me so I replaced it with a new printed piece (yes I’m a maniac, I plead guilty)
Closeup picture below reveals the pattern failure even better, next pictures are showing the piece cropped from the sail and the insert of the new part.
The sail of the real sub has some pronounced welding seams. My intention was the scribe them; I did this in the sail of my AKULA. Then I thought why don’t I actually simulate them that will be more realistic.
After a lot of try and error I manages to simulate them using 0.2mm thick fishing line.
In the below picture you see it in place, a needle is used as reference to give you an idea of the dimensions.
After this job was finished I applied multiple coats of primer, wet sanding the sail in between coats. As you might have noticed on the above pictures, in this stage I masked all the louvres, the paint would fill all the fine detail of the louvers.
Next up was addressing the scribe lines iwo the louvres, they were to deep in my opinion, applied some paint with a needle, the Capillary action did the rest. Picture below work in progress on filling the scribe lines.
After a final light coat of paint, the sail master was ready for tooling. When designing a tool you have to insure a quick and complete fill of the tool cavities. As I want to make the sail hollow a will design a two-part tool. To prevent the silicone filling the inside of the sail I sealed all openings in the sail with modeling clay (orange stuff)
Here you see the different parts for the tool that will capture the outer part of the sail. The master, the riser and the flask.
The job of the flask is to contain the rubber that forms the tool (mold) and give it rigidity during the eventual casting process. The trick is to make the flask stout, but of a geometry that will prevent excessive use of the expensive tool making rubber. Here you see the master sitting in the flask, I added two inserts to reduce the unnecessary volume.
The riser or base I use to create space underneath the sail master. This space will be used by the second part of the tool. The purpose of the created volume is to make the second part of the tool stout enough, I will come back to this later.
The picture below showing the riser covered with molding clay, this has two purposes, first it seals the sail second it adds volume.
Her you see the maters on the riser, and the riser is secured on the baseplate of the flask. Indexing knops are also in place. All sealing , securing and the indexing is done with and made out of modeling clay.
I like to degas the RTV silicone before pouring, this removes any entrapped air bubbles in the thick RTV silicone mix before pouring it into a flask. Failure to do so will result in entrapped bubbles in the hardened rubber, which will evidence as positive dimples on the surface of a pressure cast resin piece.
When pouring there is a likelihood that air bubbles will get entrapped due to the pouring. SO, I put the whole thing in a pressure chamber. This will compress any air bubbles.
Test fitting the flask in the pressure chamber.
After pouring I removed the bottom of the flask, the riser and all the gooey modeling clay. You see that the space I created by the riser now is available to pour the second part of the tool. A fresh seam of modeling clay was laid down to seal the edge of the flask with the 1 tool part.
At this stage I also added the caliper that will make the vent and sprue (vent to let air out of the tool when casting and the sprue to pour resin into the tool). Release agent was applied as RTV silicone will bond to RTV silicone.
Same pouring procedure is applied here, degassing and pressure chamber. The picture below is how the tool came out of the pressure chamber.
After opening and removing the master I ended up with the tool I need for casting the sail in resin.
All the tiny details are captured by the RTV silicone.
When the tool is assembled there is a cavity where the master used to sit. In this cavity resin is poured in trough the sprue hole, files up the cavity and pushes the air out of the cavity trough the vent hole.
I do not degas the resin. I only use the pressure chamber. The reason is that I use fast curing and I do not have the time to degas it.
The 2-component casting resin has a low viscosity, air bubbles do not get entrapped easily when the mixture is stirred up. The resin is almost water like. Air bubbles that remain the tool after casting will be compressed in the pressure pot.
Demolding the cast from the tool.
The result of the cast, a perfect replica of the master I made, all details present. Only the flash must be removed after casting and they will be ready to go in a kit-box.